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<head>
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    <title>Document</title>
    <style>
        /* input[value] {
            color: pink;
        } */
        input[value="请输入文本"] {
            color: pink;
        }
    </style>
</head>

<body>
    <!-- <input type="text" value="请输入文本">
    <input type="text"> -->
    <input type="text" value="请输入文本">
    <input type="text" value="请输入">
</body>

</html>